The invention pertains to a chain-type tool storage magazine for a machine tool, wherein a chain included in the magazine is selectively driven to position cutting tools for use by the machine tool.
In tool storage magazines of the above type, links are joined together by means of pins or other connecting elements to form a closed chain. The chain is mounted for movement along a path of travel which typically includes both straight sections and curved sections or turns, and cutting tools are attached at various positions around the chain for movement therewith. The chain is driven by a powered sprocket or other means to position selected tools in operative relationship with a machine tool.
In every common configuration of chain-type tool storage magazines, tools are mounted to one side of the chain by various means, in spaced apart relationship. The spacing between the center lines of adjacent tools mounted on the chain is referred to as "pitch". The pitch between the adjacent tools remains at a substantially constant value as the adjacent tools move along a straight section of the chain path of travel. However, the pitch between the adjacent tools will either increase or decrease as the tools are moved around a turn. A turn in the chain path of travel is referred to as an "outside turn" if the tool pitch increases, and is referred to as an "inside turn" if tool pitch decreases. Clearly, no difficulty is encountered in moving tools mounted to a side of a chain around an outside turn, since the tools move apart from one another. However, if tools are moved around an inside turn, adjacent tools move toward one another and may even clash together. To prevent this, chain-type tool magazines are frequently designed so that the chain path of travel includes outside turns only. This arrangement is exemplified by U.S. Pat. No. 3,817,391, issued June 18, 1974 for a "Tool Storage Magazine".
In a chain-type tool storage magazine having only outside turns, the chain necessarily surrounds a comparatively large amount of space which is not available for tool storage. To increase the tool storage or "tool packing" density of chain-type magazines, and thus avoid loss of valuable space close to an associated machine tool, "serpentine" configurations are employed. In such configurations, the chain is bent back and forth around a number of turns, to fill up as much space as possible. Tools are carried in sockets formed in the pins or other link connecting elements of the chain, since the pitch between adjacent link connecting elements does not change along the entire path of travel, regardless of whether the elements are moving along a straight path section or around a turn. Thus, the pitch between adjacent tools likewise remains constant over the path of travel. It will be noted that the turns in such configuration are neither outside nor inside turns, as defined above.
The above serpentine configuration improves tool packing density over other chain-type magazines of the prior art, but requires that the chain connecting elements be comparatively large or bulky. This constraint tends to result in a chain which is large and heavy, so that substantial power is required to drive the chain to selectively position tools carried thereby. The large size of the chain also increases wear and manufacturing costs, and adversely affects the speed at which the chain can be driven to selectively position a tool.